Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already convey that this is a non-read-only, non-idempotent mutation that isn't destructive. The description adds the precise effect (moving to the previous combatant), but doesn't disclose edge behavior such as what happens when already at the first combatant or whether it wraps around. No contradiction with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two short sentences with zero wasted words. The core action is front-loaded, and the use-case clarification follows immediately, making it easy to parse quickly.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a one-parameter tool whose schema and annotations already cover the safety profile and the optional combatId, the description is nearly complete. It explains what the tool does and when to use it; only niche edge behavior (e.g., starting position) is omitted, which is unlikely to affect correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There is only one optional parameter, combatId, and the schema description covers it 100% ('Combat ID (uses active combat if omitted)'). The tool description does not add parameter-level detail, but with full schema coverage and a clearly named parameter, no additional explanation is necessary.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Description uses a specific verb and resource: 'Go back to previous combatant's turn', immediately followed by the intended use case 'undo an accidental combat-next-turn'. This clearly differentiates it from combat-next-turn and from more generic combat-set-turn, so an agent can distinguish it without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly names the situation where it should be used: after an accidental combat-next-turn. It does not mention alternatives such as combat-set-turn for jumping multiple turns, but the primary use case is clearly scoped, which is sufficient for a simple tool.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.